The present invention relates to a plastic molded product having a surface layer for decoration or surface modification purposes, and more particularly to a molded product comprising a molded substrate of a polyolefin material and, provided thereon, a surface layer of a thermoplastic resin, such as an acrylic resin, wherein the surface layer is firmly adhered to the molded substrate.
Molded products produced by various molding methods including injection molding have hitherto been used in various applications. As molding materials, various resins, such as polypropylene resin and ABS, have been used according to applications. Further, a variety of molded products having a decorative design, which is provided by forming patterns, letters or the like on the surface of the molded products by printing or other methods, have also been used. In the production of molded products having a design of letters, patterns or the like, the surface on which the design is to be provided is often not flat. In this case, the so-called xe2x80x9ccurved surface printing techniquexe2x80x9d such as pad printing, and hydraulic transfer, may be used. Further, according to the simultaneous injection molding/lamination method, the production of a molded product and the formation of letters, patterns or the like on the surface of the molded product can be simultaneously carried out in one step.
Regarding molding materials, inexpensive polyolefin resins, such as polypropylene resin, are suitable from the viewpoint of cost and the like. Polyolefin resins, however, are poor in adhesion to other resins. This makes it difficult to provide letters, patterns or the like on the surface of molded products of polyolefins. Further, in general, polyolefin resins are soft and are poor in surface strength properties, such as scratch resistance. Therefore, as-molded products of polyolefin resins cannot be used in applications where a hard surface is required. Various attempts have been made to effectively decorate or modify the surface of the molded products of polyolefin resins, e.g. for the purpose of enhancing the surface hardness, so that the polyolefin molded products can be utilized in wider applications.
For example, there is known a method {circle around (1)} in which a surface coating is applied onto a polyolefin molded product. This method can effect a surface modification of a molded product to improve the surface strength, etc. However, it is not possible with this method to decorate a molded product by providing letters, patterns or the like on the surface thereof.
Also known is a method {circle around (2)} in which a primer is coated on the surface of a molded product to improve its adhesiveness, followed by decoration of the surface by the hydraulic transfer method. Though this method can provide a molded product with letters, patterns or the like, the letters or the like are likely to be undesirably distorted. Further, this method necessitates two coating steps, i.e., the primer coating and a top coating after hydraulic transfer of a paint, leading to low production efficiency and high cost.
Further, in methods {circle around (1)} and {circle around (2)}, a coating composition having good adhesion to the polyolefin resin should be selected.
There is also known a method {circle around (3)} in which simultaneously with molding of a polyolefin resin, a surface cover sheet, such as a decorative sheet, is laminated onto the as-molded product (simultaneous injection molding/lamination method). In this method, use of a surface cover sheet with a polyolefin resin sheet laminated onto the backside thereof can offer improved adhesion, and will provide a molded product with a surface cover sheet firmly laminated onto the molded substrate. However, the step of laminating a polyolefin resin sheet onto the backside of a surface cover sheet will increase the production cost. Further, the presence of the polyolefin resin sheet in the surface cover sheet will enhance the breaking strength at room temperature. This makes it difficult to cut the sheet at the time of trimming of excess sheet after the lamination step.
Accordingly, it is an object of the present invention to provide a molded product which utilizes an inexpensive polyolefin-based material as a molding material and which has a cover layer for surface modification, decoration or other purposes, which cover layer is firmly adhered to the molded substrate.
The above object of the present invention can be attained by a molded product comprising: a molded substrate comprising a polyolefin resin and an ethylene-propylene rubber; a chlorinated polyolefin resin layer laminated onto the molded substrate, the chlorinated polyolefin resin layer being in contact with the molded substrate; and a surface layer of a thermoplastic resin laminated as an outermost layer onto the chlorinated polyolefin resin layer either directly or through other layer(s). According to this molded product, by virtue of the ethylene-propylene rubber contained in the molded substrate and of the chlorinated polyolefin resin layer laminated in contact with the molded substrate, the surface layer is laminated with good adhesion onto the molded substrate.
In the above molded product, when the surface layer is formed of an acrylic resin, a urethane resin layer may be provided between the surface layer and the chlorinated polyolefin resin layer such that it contacts at least with the chlorinated polyolefin resin layer, whereby the adhesion between the surface layer and the chlorinated polyolefin resin layer can be improved.